Transmission dynamometer



Oct 21,1941. H. KUEHNI I 2,260,036

TRANSMISSION DYNAMOMETER Filed' Aug. 24, 1940 -Pig. I.

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Fig. 3. dd Z/ 24' w 42 2a 2. 2; 1'4", 7 l 7 7 J9 mu l/011w M Fig 4 g V 4'9 t Y I 7 55" I J" I I 26" I 6i" 2 y a r Inventoh:

4v Hans P. Kuehni, u by WW6. I at His Attorney.

= spect to the shaft as an axis to Patented Oct. 21, 1941 H UNITED STATES "PATENT OFF-lCE 2,200,030 'raansivnssron DYNAMOMBTEB Hans r. Kuehni, Schenectady, N.

1., assignor to (irer'ieralv Electric Company, a corporation of New York Applicatlon Augnst 24 1940, Serial No. 354,102 '1 Claims.. (,01. sass-e) This invention relates to transmission dynamometers and more particularly to transmission dynamometers for electrically measuring the torque, horsepower, and horsepower-hours transmitted by a mechanical shaft.

It isan object of my invention to provide an improved transmission dynamometerfor. electrically measuring the torsional force and power in arotating shaftand, if desired, the energy expended over a period of time.

It is another object of my invention to provide an improved transmission dynamometer in which the measuring elements are so positioned with resubstantially eliminate design difliculties in overcoming centrifugal forces.

It is a further object of my lnvention'toprovide an improved transmission dynamometer whereby the torsional twist of they power transmitting member is translated into longitudinal displacements, the measurements of which are proportional to the torque transmitted.

In carrying out my invention in its preferred. iorm I provide a hollow shaft element of generally cylindricalform which is adapted to be positioned intermediate the driving element and the driven member for transmitting the driving torque. spaced helical slotsformed in the surface thereof on one side of an intermediate portion and has similar spaced helical sl'ctsformed in the surface thereof on the opposite side of the intermediate portion. The slots on one side of-the intermediate portion of the hollow member are in the lefthand direction while those formed on the other side are in the righthand direction; each case being preferably arranged such that their pitch angle transmission of power through the hollow element theinterm'ediate portion undergoes an axial movement, the direction ofwhich is dependent upon. the direction of the, torque transmitted. I a pair of electric gage elements-which are preferably arranged along the axis of the shaft and inside the hollow member for obtain-. ing indications in accordance with the longitudinal movement of the intermediate section of the hollow member. These gage elements areconnected in an electrical circuit whereby indications are obtained proportional to the torque transmitted. If desired, a voltage may be derived which is proportional to thespeed of the shaft and by the employment of'a wattmeter type instrument having one element energized in accordance with torque and the other element enerthe appended erence to the following description taken in con- The hollow member has a plurality of showing twohelical springs, one hand type and the other of the lefthand type 5 partly the slots in is substantially Uponthe 0 substantially all of the torque.

similar tothe disk M and member serving to gized in accordance with speed, indications proportional to horsepower may be obtained. Also, if desired, an integrating type measuring device may be employed to provide a measurement of the horsepower hours expended over a period of time. I

In a modification, foregoing type is floatingly positioned within a larger hollow cylindrical member, the, latter transmit the actual power. In this case, the hollow member provided with the helical slots may be made relatively small since it depends for its operation. upon the mechanical twist which takes place in the larger torque transmitting element. The electric age torque measuring element therefore measures the longitudinalmovement of the central member as determined by the twist angle of the larger element. Y

The nov my invention 1 features which are characteristic of are set forth with particularity in claims. My invention itself, however, both as to its organization and method of operation together with further objects andadvantages thereof may best be understood by refnection with the accompanyin d awing.

In the drawing Fig. l is a schematic diagram of the rightfor the purpose of illustrating the principle of my invention. Fig. 2 is a longitudinal view in elevation of apparatus arranged in accordance with s 3 is a longitudinal view, in cross section, of the torque transmitting element of Fig. 2. Fig. 4- is a' modification in which a relatively small hollow measuring element with slots form'e'd therein is positioned within a larger hollow element which transmits my invention. Fig.

elevation view of the apparatus shown in Fig. 4, and Fig. 6 is a diagram of electrical connections which shows a manner of connecting the gage coils in an electrical circuit for obtaining lndica tions in accordance with the torque, horsepower,- and horsepower hours transmitted between a driving and driven element.

Referring to Fig. l, in principle of my invention, I have shown-two coil or helical springs II and l2.- The coil spring i. having a righthand hell! is fastened at one end to a disk it and at the other end to an intermediate disk it. The coil spring I! having a lefthand helix is'fastened at one end to a disk II to the opposite'side of the hollow member of the.

Fig.5isanend order t'o illustrate the of. thei'member 28a structing the parts for the intermediate disk l6 from that which supports one end of the coil spring II. In the form shown the springs are rectangular in cross section. If it be assumed that the two outer disks l4 and it are maintained at a constant distance from each other and that torque is transmitted through the system, the intermediate disk l6 will move axially in one direction or the other as shown by the arrow 2!, the direction being determined by the direction of the torque, because of the fact that the coils or springs ill and i2 tend to shorten or lengthen. respectively, depending upon the torque applied. The direction of movement also depends on whether the helical members are constructedso that the stiflness is, greater in the axial direction than in the radial direction or vice versa. The amount of movement the central disk ii for a given torque depends upon springs and the angle of each helix.

In Figs. 2 and 3 I have shown the Iundamen tal principle 0! Fig. 1 translated to an actual power transmitting shaft by the provision of a hollow member is provided with apertures 24 and ed with lefthand spaced righthand helical slots or theA-righthand portion is providspaced helical slots or apertures 28. The slots may conveniently be formed by a milling machine. The central portion of the hollow member 22 whichlies intermediate the slotted sections and which corresponds to the central disk l6 0! at 28. In the arrangement illustrated, the opposite end portions 29 and 30 of the hollow member or torsion device 22 are mounted in suitable bearing elements 3| and 32 connected by suitable coupling devices II and 34 to shaft sections 35 and. 36 one of which is connected to a power source andthe other or which is connectedto a power absorbing device. It is assumed that all thrusts in the direction of the longitudinal axis of the shaft are taken up by the couplings and the bearing elements.

In order to obtain indications proportional to the axial movement of the central or intermediate portion 28 of the hollow torsion element 22 I provide a pair of electric gage' elements 38 and 4B which include current coils 42 and 44 and magnetic'cores 4G and 48 are arranged within the intermediate section 28 and are symmetrically disposed on opposite sides of 28a 01 magnetic material to member air gaps member 280. may ilt or by other suitable means. The magnetic cores 46 and 48 and the disk-like member 28:: are preferably form with the-latter ill and 52, respectively.- The the shape of the cross section of the coil' 22 in which the lefthand portionand are adapted to be be secured in position by a pressv Fig. 1 is left solid as indicated composed of a suitable magnetic material in laminated or solid form having rela-' tively high permeability and. low coercive force, such for example as soft ironor other well known materials. It will be appreciated that the member 28a may be formed integrally with the secnetic inseltsrmay be positioned on opposite sides to cooperate with each of the cores 4B"and 48.. I

While 1 have shown helical; members or elements made integrally with the shafi member 22 including the section 28,

, arranged with a pitch angle 0 and have described them as being formed by a milling operation, I'yvish to point out that this is merely an illustration of a -manner oi concarrying out my invention. For example, the

a disk-like member 5 out to a plurality of slip rings composed of separate springs or helices and each Joined to an intermediate member and a member or element at each end.

The gage coils and cores are securedto studs 7 or rods 83 and 54 each of which is mounted at opposite ends of the torsion element 22 in a plug member I which is provided with screw threads 58 adapted ,to engage the interior of the hollow member 22. The rods i! and 64 are provided with screw threads I! which engage the threads in a nut 58, the latter being secured in position to the plug 55 by a plurality of screws 59. A longitudinal keyway 6! adapted to accommodate'a key 6| provides means for preventing rotation of the rods 52 and 84 relative to the plugs 55. Withthis arrangement the position oi the gage elements 38 and 4| may be adjusted lengthwise to properly proportion the air gaps i0 and I2 without the rods 52 and 84 merely by loosening the screws It and rotatingthe nut 58. A lock nut 52 series circuit relation interiorly oithe hollow-torsion member 22 with their end terminals-and a connection at-their Junction brought spectively. V

In the modification shown. in Figs. I have shown a slotted ilar to the element 22 considerably lighter requiredto transmit 4and 5,

but which may be made of material because it is not the actual load torque, In

plate may be connected conveniently with the hollow member This arrangement has the advantage that the same torque element 22' can be employed with a plurality oi main torsion elements 68 01' different sizes. I

In the construction of the hollow torsion elements 22 and 22', for most satisfactory results,

the right and leithand u helical elements may be ameter and shorten the helical slots 24, 2 and 24', 26' are preferably substantially 45.

3, 64 and 65, re-

element22' which is sim-- v operation of the Thus when a control omitted-.-the instrument M section 36.

flowing through elements are arranged near.

length increased,- thereby causing movement of the central portion 28 to the left. So far as the device is concerned, however, each helix may be constructed with the long sides of the rectangle lying in planes perpendicular to the axis of rotation, in which case *the helical sections will be relatively stifi in the radial direction. Such an arrangement will resist change in diameter when torque is applied but the pitch and length will change. The motion along the rotary axis of the central torque will be relatively opposite in the two cases.

In Fig. 6, I have illustrated a manner of connecting the gage elements in an electric circuit member 2811 for a given Consequently,

- operation for obtaining indications in accordance with the movement of the intermediate member 28a. In this arrangement, the coils 42 and it are shown connected in adjacent arms of a Wheatstone bridge circuit, the remaining arms of which are formed by sections 14 and 16, respectively, of a differential reactor 18. The. bridge isenergizedby a suitable source of alternating current 80. The outer terminals of ed. to an electrical indicating instrument '82 through a full wave rectifier element 8%. If it is desired to record the variations in torque, a recording element such for exampleas an oscillograph or other recording device 86 may be connected to the output terminals of the rectifier element 8E.

In the event 'that it is desired to obtain measurements of the horsepower or horsepower hours transmitted I may provide a pilot generator 88 preferably having a permanent magnet field and which is mechanically connected to the rotary shaft and adapted to generate a voltage proportional to the "speed. The letter M designates a meter either oi the integrating type or of the wattmeter type of any suitable construction having one element thereof connected to the pilot generator 86 and the other element connected to the output terminals employed in the meter M the indications will then be proportional to the horsepower transmitted. While if the meter M is of the integrating type-in which case the control spring is will register the energy expended over a period of time;

In operation, assume that the shaft element is rotating in a clockwise direction as viewed from the lefthand end of the shaft to transmit power to a driven member connected In this case, for the particular cross section shown of the 28 of the hollow shaft 22 will move toward the left thereby increasing the air gap Hand decreasing the air gap to change the relative reluctance of thetwo magnetic circuits which are energized by the gage coils. and 42. As a result, the relative impedance of the gage coils changes and the condition of balance or degree of unbalance is altered in accordance with the movement,-nf ..the. intermediate member 28a, resulting in cori esponding changes in the current the instrument 82 and the meter M.

I have thus provided a transmission dynamometerg eluding a hollow torsion element of novel construction which is adapted to be positioned to respond to torsional forces required to drive a load. The

the advantage that the torque pickup or gage the 'center of' thethe bridge are shown connectunderstood that axially spaced from eachother at the other end shaft and-they have perfect radial symmetry.

the torsion shaft may be operated at high speeds without introducing design difiiculties due to centrifugal forces.

' In accordance with the provisions of the Patent Statutes, I have described the .principles of of my invention together with the apparatus which I now consider to represent the best anbodiments thereof but I desire to have it the apparatus shown and described is only illustrative and'that the invention may be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a transmission dynamometer for transmitting power from a driving member to a driven member, a first element and. a second element and adapted to undergo a relative angular displacement in proportion to the torsional force required to drive said driven member, an element positioned intermediate said first and second elements and adapted to move in an axial direction relative thereto, a righthand spring helix secured at one end to said first element and at the other end to said intermediate element, a lefthand spring helix secured at one end to said second element and I to said intermediate element, whereby one helixis caused to lengthen and the other to shorten and said intermediate member is caused to undergo movement relativetosaidfirst and second elementsin the direction of the axis of rotation thereof proportional to the angular displacement between said first and second elements, and means' responsive to said relative movement.

mitting power from adriving member to a driven of the rectifier element 84. spring or the equivalent is.

to the shaft helices, the central section 3 low shaft element arrangement as shown has to lengthen and member, a torque responsive device adapted to be positioned between said driving and driven members, said torque responsive device comprising a first element and a second element axially spaced from each other and adapted to'be connected one to said driving member and the othertov said driven member, means for mounting said first and second elements in a manner permitting rotation but preventing relative movement thereof in an axial .direction, said torque responsive device further comprising a tioned intermediate said first and second elements and free to move in an axial direction, a righthand spring helix secured at. one end to said first element and at the other end to said third element, a lefthand spring helix secured at one end to said second element and at the other end to said third element, whereby one helix is caused the other to shorten and said third element undergoes a movement in the direction of the axis of rotation in. proportion to the angular displacement between said first and second elements, and means for measuring the axial movement of said third element.

3. In a transmission dynamometer for trans-. mitting power from a driving member to a driven member, a hollow shaft element in the general form of a cylinder adapted to be positioned bedriving and driven members; said holbeing supported for rotation. at'each of its'ends in a manner to prevent relative axial movement between said end portions, said hollow member. having a plurality of spaced righthand helical slots formed therein between one end and an intermediate section'thereof and tween said having a plurality of spaced lefthand helical slots formed therein between the other end and said third element posi- .ment and subject to andaxiallymovable current conducting intermediate section, whereby said intermediate section undergoes a movement in the direction or the axis of rotation in proportion to the torque transmitted through said hollow member, .and

" means responsive to said axial movement.

4. In a transmission dynamometer for transmitting power from a driving memberto a driven member, a shait element positioned intermediatesaid driving and driven members said power and adapted to undergo a torsional twist in accordance with the torsional force required to drive said driven member, a torque responsive device comprising a flrstelement and a second element, said elements being secured to said shaft element at axially spaced points thereof and adapted to undergo an angular displacement with respect to each other proportional to the twist in said shaft element, said torque re-, .sponsive device further comprising a third element positioned intermediate said first and secand elements and adapted to move axially rela-- tive thereto, a righthand helix rigidly secured at one end to said first element and at the other end to said third element, a leithand helix rigidly for transmittingsaid hollow member movement in the axial direction relative to said 30 first and second element; proportional to the relative angular displacement of said first and sec-e ond elements, and means responsive to said axial movement.

5. In apparatus or the class described, a hollow member of generally cylindrical form arranged ior transmitting tween a driving member tions of said hollow mounted but restrained mechanical power hemember being rotatably respect to each other in accordance with the torque required to drive said load, said hollow member having a portion thereof lying between one oi said end portions and an intermediate Portion thereof cut away to form a plurality of aperturestherein, magneticmaterialposifloned hollowmemberandmtatably means composed of internally of said magnetic material and a load, the end porwithsakiintermedlatopor-- from relative axial move- 0 angular displacements with measurement to drive said i 6. In combination in apparatusoi the class describedra hollow member oi generally cylindrical i'orm mounted tor rotation and arranged in such a way that its end portions are subjected to a relative angular displacement in proportion to the torsional'i'orce required to drive a load, said hollow member having a plurality of spaced righthand helical slots formed therein between one end and an intermediate section thereof. having a plurality oi spaced lefthand helical slots formed in the portion of its suriace lying between the other end thereof and said intermediate section, whereby said intermediate section undergoes a movement along the axis of rotation in proportion to the relative angular displacement of said end portions, a member composed of magnetic material secured to said intermediate section, electromagnetic means comprising a magnetic core .and an electrical coil, said core being arranged in spaced relation with the magnetic member and said spacing being variable in accordance with axial movements of said intermediate section, said coil being adaptedto be energized with alternating current for sending magnetic flux through said magnetic core and said magnetic member, and means operable in accordance with reactancc changes in said coil causedby variations in the spacing of said core and said magnetic member.

7. In a transmission dynamometer for transmitting power from a driving member to a driven member, a torque transmitting element interposed betweensaid driving and driven elements and having its pposite end portions connected respectively to said driving and driven members. means i'or mounting said torque transmitting element at its -.end portions in a manner to permit rotation and to restrainsaid end portions fromrelative axial movement, said torque transmitting element comprising lefthand and righthand helical elements positioned intermediate said end portions and connected by an axially aligned intermediate element tel-mediate element undergoes an axial displacement relative to'said endportions when said end inrdativelyopposite' uponaxialmovcnmtotsaklintermediateportiomandmansopernhleinloeordanee withrelativechangeeinthemchneesotlaid windings for portions are subiected to an ular displacements with respect to each other in accordance with the torque transmitted tosaid driven member. elecric gage means comprising magnetic circuit members and electrical winding means for magnetic flux in said magnetic circuit one.or said magnetic circuit members being mounted to move-axially with said intermediate element, said ranged in Whitewater-MM.-

whereby said in CERTIFICATE OF CORRECTION. Patent No.- 2,260,056. October 21', "19!;1.

HANS P. KUEHNI.

It is hereby certified that error appears in the. printed specification of the above numbered patent requiring correction as follows Page 2, first coiumn, line 149, after "I18" insert respectively. The magnetic cores Lp'and L B- page 1;, second column, lines 15 and 11L,C18.im 6, strike out "in the portion of its surface lying" and insert instead therein--; and.

that the said Letters Patent should be read with this co'rrectiontherein th t the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of December, A. D. 191;.1.

7 Henry Van Arsdale, (Seal) Acting Commissioner of Patents. 

